Actual Rotary Displacement Request

[RICE RACING]

I decided to put this together for the new players who struggle with understanding what a wankel cycle is about and also the true capacity of the engine, a picture tells a thousands words, so I cut up a rotor and a shaft and marked them taking a photo at every 90 degree's of main shaft rotation, following a chamber from firing to firing or one full Wankel Combustion Cycle.

0 degree's TDC No1 chamber firing


90 degree's


180 degree's


270 degree's


360 degree's (one revolution of crank)


450 degree's


540 degree's


630 degree's


720 degree's (two revolutions of crank)


810 degree's


900 degree's


990 degree's


1080 degree's Wankel Cycle is complete ! (after 3 full revolutions of the crank shaft) No1 chamber firing again


From the above you can see each individual separate chamber (3 per rotor) only fires after 1080 crank shaft degree's has elapsed,, this is why the Wankel is so different to ANY other type of engine, 2 strokes fire each individual chamber once every 360 degree's and 4 strokes fire every individual chamber every 720 degree's.

If you look at a 13B with its 654cc per Individual chamber capacity (thus 1308cc) you can see it aspirates this ONCE every single revolution thus you can compare the 13B to a 2 stroke if you must do so on an equivalence basis (but remember you are not counting the other 2/3rd's of the combustion faces!

Now if you compare it to the much more common 4 stroke engine you can see that 2 faces ONLY are being counted in the engine and thus it has aspirated a total of 2616cc over 720 degree's of crank shaft rotation....... nice little bit of info there but it still misses a whole 1/3rd of the engine!

Finally the ONLY TRUE way to look at a Wankel Rotary is to view it in its own cycle! (and not comparing it to something that it is NOT!) this is only over 1080 degree's of crank shaft rotation, where ALL of the working faces can be accounted for (just as when you do a compression test to see if the poor little donk is healthy or not) For it is only when the entire engine has complete one full cycle of work can it thus be rated, be that as functional or in its true capacity sense. You will then see that the humble 13B is indeed 654cc x 3 working faces x number of rotors ! = 3924cc.

Equivalence capacity to time scale (revolutions) for 13B engine, has one power pulse per 360 degree's per rotor
1308cc 360degree's (2 stroke)
2616cc 720 degree's (4 stroke)
3924cc 1080 degree's (Wankel Rotary)

[My5ABaby]

Would apples to apples be hp/lb (of engine weight)?

[Barry Bordes]

Yes Peter I agree that it would take three revolutions of the eccentric shaft to have all faces of the rotor see fire.

Following that logic the other trochoid shapes would need four or five revolutions to show all faces and hence we would have to multiply them by 4 or 5.

I am saying that in all of these shapes that the displacement is the volume of the largest cavity created by the two corresponding surfaces (actually 4 counting end plates).

This would hold true for a two-stroke and a four-stroke also.



As an example the caliber of this revolver doesn't change if it holds different numbers of slugs. It is still a 357.

[RICE RACING]

Barry, ALL of the total sum faces fire once in 1080 degree's, nothing more nothing less.

Like I tell my students, you need to take time out and see the pictures, if you don't get it at first do not worry you are not the first and not the last to get confused on how internal combustion engines work.

2 stroke
4 stroke
Wankel

Its pretty simple really.

[RICE RACING]

For EVERYONE remember this.

In 360 deg
ALL CYLINDERS in a 2 stoke fire once! no matter if its single or a V16!

In 720 deg
ALL CYLINDERS in a 4 stroke fire once! no matter if its a single or a V16!

In 1080 deg
ALL faces of a rotary wankel fire once! no matter if its a single rotor or a 4+ rotor!

Which ever formula you decide to use in your PISTON applications you need to know which EQUIVALENCE displacement to use (2 stroke, 4 stroke or wankel) there are no aftermarket ECU's set up to run the true Wankel cycle or count the individual rotor faces based of its ACTUAL cycle (which is only 1080deg, nothing less)......... so you just need to know how a motor works and apply the other piston engine formulas to the wankel as appropriate (as I showed all of you)

[Libor]

Originally Posted by RICE RACING

there are no aftermarket ECU's set up to run the true Wankel cycle or count the individual rotor faces based of its ACTUAL cycle

Peter, I was curious about something. Would there be any benefit in engine control with ECU of such abilities? Like better fueling of individual chambers?

[RICE RACING]

Originally Posted by Libor

Peter, I was curious about something. Would there be any benefit in engine control with ECU of such abilities? Like better fueling of individual chambers?

There are some of us who are using this kind of bespoke *aftermarket* true rotary ECU and have been doing so for a long time!

Yes there are major benefits!
Mazda racing ECU's and stock ECU's are of this type 1080 deg true Wankel cycle, it is the only way to truely look at the engine.

Otherwise you do need to do alot of conversions to adapt all the other ECU's, not to hard to do, but most dont get it, especially when you are looking at things like control of injector opening and closing degree's etc.

[Barry Bordes]

Originally Posted by RICE RACING

Barry, ALL of the total sum faces fire once in 1080 degree's, nothing more nothing less.

Like I tell my students, you need to take time out and see the pictures, if you don't get it at first do not worry you are not the first and not the last to get confused on how internal combustion engines work.

2 stroke
4 stroke
Wankel

Its pretty simple really.

Actually example (3) (shown below) would take 1440º and

example (4) would take 1800º to complete all faces of its trochoid shape.

Different rotor/stationary gear ratios would be used to accommodate the 4 in 3 and 5 in 4 trochoid mesh.

Barry

[RICE RACING]

I am ONLY refering to the Wankel Rotary I pictured and as we all use, drive and modify

Nothing else

[Monkman33]

Guys, displacement by definition is the volume displaced by one revolution of the crankshaft or e-shaft in this case. doesn't matter if it is 2 stroke, 4 stroke, or not.

You guys are all going off on this "when does it ignite, and when does it do this or that?" It's all moot.

total volume displaced over 1 crankshaft revolution = Displacement. It is consistent across the board. There is no Mazda conspiracy to hide its actual displacement. A 6.0 liter engine is a 6.0 liter engine, whether its 2 stroke or 4. You can't use the "Getting back to face 1" argument due to the trochoidal nature and the 3:1 ratio. If you do use this argument, then you have to divide the final result by 3 because of the 3:1 ratio.

Now, what is the one consistent thing in all the engines? output RPM. Displacement is based on 1 of these revolutions. So any other attempt to define definition by more than 1 revolution is incorrect. 1 revolution is the consistent factor across the board. Te reason racing bodies use a multiplier is to even the playing field just like they do for 2-stroke engines. The advantage a 2 stroke has is that is happens to fire its full displacement per revolution, just as a rotary does, where as a 4 stroke only fires half of its displacement per revolution.

Don't confuse revolutions of the rotor versus the crank/eshaft. You'll end up chasing ghosts.

[RICE RACING]

It's not a argument, its FACT! ALL INTERNAL COMBUSTION ENGINES (except the rotary!) are rated on ONE CYCLE OF WORK FOR THE COMPLETE ENGINE.

Mazda conveniently choose to not rate the whole engine, if you or others can't get that then you need to move onto another area of interest I suggest, one you can understand

The Wankel Rotary is a 1080deg cycle, nothing more nothing less!

You btw f*** your own argument cause a 4 stoke is NOT rated after only 360 degrees! cause it HAS NOT COMPLETED ITS CYCLE OF OPERATION! it is rated ONLY AFTER 720 degree's (suck sqeeze bang blow) it only SUCKS once in 720 degree's! and ALL piston faces are counted to rate the displacement of the whole engine! not 1/3rd of them, or 2/3rd's of them! but ALL OF THEM!......... The irony is only in the rotary world where people want to only count 1/3rd of the combustion faces and rate it as a 2 stroke engine, but its NOT! its a wankel and thus they only want to count one face (which misses out 2/3rds of the rest of the engine). if only you could do this on a BDC built half bridge!!!! then when it drops an apex seal on each rotor he can then tell you its only a 2 stroke engine like people in this thread and the other 2 apex seals and four combustion faces are not required LOL!!!!!!!!!!!

[Barry Bordes]

Originally Posted by RICE RACING

It's not a argument, its FACT! ALL INTERNAL COMBUSTION ENGINES (except the rotary!) are rated on ONE CYCLE OF WORK FOR THE COMPLETE ENGINE.

Mazda conveniently choose to not rate the whole engine, if you or others can't get that then you need to move onto another area of interest I suggest, one you can understand

The Wankel Rotary is a 1080deg cycle, nothing more nothing less!

You btw f*** your own argument cause a 4 stoke is NOT rated after only 360 degrees! cause it HAS NOT COMPLETED ITS CYCLE OF OPERATION! it is rated ONLY AFTER 720 degree's (suck sqeeze bang blow) it only SUCKS once in 720 degree's! and ALL piston faces are counted to rate the displacement of the whole engine! not 1/3rd of them, or 2/3rd's of them! but ALL OF THEM!......... The irony is only in the rotary world where people want to only count 1/3rd of the combustion faces and rate it as a 2 stroke engine, but its NOT! its a wankel and thus they only want to count one face (which misses out 2/3rds of the rest of the engine). if only you could do this on a BDC built half bridge!!!! then when it drops an apex seal on each rotor he can then tell you its only a 2 stroke engine like people in this thread and the other 2 apex seals and four combustion faces are not required LOL!!!!!!!!!!!

OK, so my guess is that this is a 2499 magnum!

[Monkman33]

Originally Posted by RICE RACING

It's not a argument, its FACT! ALL INTERNAL COMBUSTION ENGINES (except the rotary!) are rated on ONE CYCLE OF WORK FOR THE COMPLETE ENGINE.

Mazda conveniently choose to not rate the whole engine, if you or others can't get that then you need to move onto another area of interest I suggest, one you can understand

The Wankel Rotary is a 1080deg cycle, nothing more nothing less!

You btw f*** your own argument cause a 4 stoke is NOT rated after only 360 degrees! cause it HAS NOT COMPLETED ITS CYCLE OF OPERATION! it is rated ONLY AFTER 720 degree's (suck sqeeze bang blow) it only SUCKS once in 720 degree's! and ALL piston faces are counted to rate the displacement of the whole engine! not 1/3rd of them, or 2/3rd's of them! but ALL OF THEM!......... The irony is only in the rotary world where people want to only count 1/3rd of the combustion faces and rate it as a 2 stroke engine, but its NOT! its a wankel and thus they only want to count one face (which misses out 2/3rds of the rest of the engine). if only you could do this on a BDC built half bridge!!!! then when it drops an apex seal on each rotor he can then tell you its only a 2 stroke engine like people in this thread and the other 2 apex seals and four combustion faces are not required LOL!!!!!!!!!!!

Wow.... you are so off base its amusing.

ALL engines, 2 stroke, 4 stroke, rotary... are using only one rotation of the crank shaft to measure displacement.

If you use your logic, then the 6.0 liter ls2 engine would really be a 3 liter 2 stroke engine if you built a custom head for it and ignited fuel every revolution? ... I am sorry, but you are wrong. The bore and stroke never changed therefore, your logic is home to a MAJOR fallacy.

Wow.. you are arguing that somehow the method of measuring displacement has anything to do with which apex seals are required. To measure the displacement of a rotary engine, you would total the amount of volume displaced by one face of each rotor and add it up.

Just like in a piston engine, you would take the displaced volume of EACH cylinder (notice how 4 stroke or 2 stroke doesn't matter) and add them together.

Displacement calculation DOES NOT take into account how many revolutions it takes to actually fire each piston or rotor face. I have a lot of respect for you rice racing, but you are very far off base here. Displacement caluculations are simple:

How much volume is displaced by the engine (regardless of type) in 1 rpm of the crankshaft/eshaft IS your displacement. Its fact, non-arguable.
You can do displacement calculations without the heads on. it doesn't matter if it is 2 or 4 stroke. Hence why they do all 2 and 4 stroke piston engine calculations like so: stroke x bore x # of pistons = displacement. which would be the EXACT same as: displacement of each piston added together x 1 rpm. The 1 rpm factor must remain the same between all engines to have an effective and consistent method of calculating displacement.

[NoDOHC]

Peter and Barry, I have too much respect for both of you to stand idly by while you dispute so vehemently.

It's Ok to disagree, but let's not turn this into an personal argument. This is a case where the only important factor is that we understand how the engine works. It is accurate to say that a rotary engine completes an intake, compression, power and exhaust stroke on each rotor during a single rotation of the engine. However it requires 3 revolutions of the engine for all faces of each rotor to see all four strokes.

The difference between you is that Barry is looking at a single rotor housing as the displacement-providing chamber, while Peter is looking at the rotor as the displacement-providing chamber. Neither of you is right or wrong, it is a difference of perception.

How each of us slices this up depends on personal preference and nothing more. There is no right answer here.

I appreciate the information and clarification provided in this thread, but I don't want two knowledgeable and intelligent members of this community bogged down in this senseless argument.

Let's leave it with the cycle explanation and keep this thread informative.

[diabolical1]

Originally Posted by NoDOHC

Peter and Barry, I have too much respect for both of you to stand idly by while you dispute so vehemently.

It's Ok to disagree, but let's not turn this into an personal argument. This is a case where the only important factor is that we understand how the engine works. It is accurate to say that a rotary engine completes an intake, compression, power and exhaust stroke on each rotor during a single rotation of the engine. However it requires 3 revolutions of the engine for all faces of each rotor to see all four strokes.

The difference between you is that Barry is looking at a single rotor housing as the displacement-providing chamber, while Peter is looking at the rotor as the displacement-providing chamber. Neither of you is right or wrong, it is a difference of perception.

How each of us slices this up depends on personal preference and nothing more. There is no right answer here.

I appreciate the information and clarification provided in this thread, but I don't want two knowledgeable and intelligent members of this community bogged down in this senseless argument.

Let's leave it with the cycle explanation and keep this thread informative.

^ this!

i'm not an engineer. i have mechanical experience, but no paper credentials. i just want that out of the way before i offer my thoughts.

i've read through this thread a couple times now (and i read the rotarygod link last night) and it seems to me that no one of these assertions is wrong because they clearly state the context for which they claim.

the 1308 chamber derivation is irrefutable. the 2616 argument is just as valid in the context of the 2 rotor derivation. finally, the 3924 is also valid in terms of absolute displacement because it's the only conclusion that takes all 6 chambers into account regardless of their phase during a crank rotation.

i think the only true argument left is which, if any, is MORE right. i'm not qualified to make that determination. hell, i'm still trying to find out how 80 and 240 yield 1308. however, while i don't dismiss any of the others, i will say that i'm tending to lean toward the 3.9 assertion now. i think a part of the lingering ambiguity is simply us not knowing when and where to draw the line with the reciprocating engine comparisons. rotaries are different, there's no getting around that.

the points made for 3.9 are compelling (to me) simply because none of the piston calculations leave any cylinder uncounted, while the 1.3 and 2.6 assertions for the 13B do. that said, none of the piston calculations require 3 revolutions - though, in all fairness, revolutions are not relevant. when you plug bore and stroke numbers into the volume of a cylinder formula, then multiply by the number of cylinders, none of that takes revolutions of the engine into consideration. it's just the number for the engine's absolute capacity. crank lobe angles/phasing have no bearing. my MR2 Turbo was 1998 cc, not 500. my Audi engine is 2671 cc, not 445.

as for the dust-up, by now Rice should know i respect him very much. i actually like his un-PC style, it's a breath of fresh air to me - not to mention sometimes it's just bloody hilarious (see my sig ). being somewhat socially inept myself, i won't comment on his interpersonal skills and i certainly won't judge him, but i think he should just step back and reasses the discussion. i don't see where anyone attacked or offended him (i know its not my call, but it is my observation) so he should return to the discussion with no hard feelings.